JPH11345133A - Input/output control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an input/output control system, in which the difference of priority is not changed by the number of processing queues, a processing waiting list is not required for each priority level and the need for passing monitoring or duration check control is eliminated. SOLUTION: When an input/output processing waiting list is formed, the list is not divided for each priority level, but all the queues are registered on one list. A pointer is provided for instructing the queue located in the middle of the queue list of low-order priority levels registered on the list, and when the queue having high-order priority is generated, the generated high-order priority queue is inserted at a position before the queue instructed by that pointer. When executing processing, the queue is simply extracted from the head of the list, and a request is processed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input / output control method used in a computer system, which has a function of realizing priority control by a simple mechanism using a waiting queue list.

[0002]

2. Description of the Related Art As shown in FIG. 1, when an input / output request is generated from a program 1 to 3 for executing parallel processing, a request receiving mechanism 5 receives the input / output request, and a request selecting mechanism 6 receives the input / output request. The request is selected and the input / output processing is executed in the request processing unit 7.

[0003] In this series of processing flows, the request receiving mechanism 5 and the request selecting mechanism 6 perform processing according to the following logic.

When forming an input / output processing queue, as shown in FIG. 2, processing queues are linked by bidirectional pointers in the order of processing request generation to form a doubly linked circular list. When a processing request is generated, the request is registered in a queue, and the queue is linked to the end of the list (queuing).

[0005] When performing the processing, the processing is performed by removing it from the head of the list. As a result, first-in first-out (FIFO) is realized. In this case, the priorities (priorities) of the queues waiting for processing are all the same, and processing is performed in order from the one that issued the request as soon as possible.

Here, in order to give priorities to processing requests, it is necessary to divide the list for each processing having the same priority. A list to be processed is selected in consideration of the priority when executing the processing. For example, it is assumed that two levels of priority levels P0 and P1 are provided in the execution of a certain process. Here, P0
It is assumed that a process having a priority of P1 has a higher priority to be executed than a process having a priority of P1.

In this case, when a processing request is generated, the request is queued in a list corresponding to the priority, as shown in FIG. When executing the process, the queue of the P0 list is processed twice consecutively in the order of queue 1 → queue 2 → queue 6 → queue 3 → queue 4 and then the queue of the P1 list is processed.

In this method, the difference in priority changes depending on the number of queues to be processed. As shown in FIG. 4, it is assumed that the number of processing queues queued in the list on the P1 side is much larger than the number of queues on the P0 side. In such a state, the processing request A (P0
In the case where two processing requests are generated, the processing request B (P1 level) and the processing request B (P1 level), the processing request A is processed much earlier than the processing request B because the processing order is fixed. In this case, P0 has a much higher priority than P1.

On the other hand, as shown in FIG.
If the number of queues to be processed is greater than one, processing request A
(P0 level) and processing request B (P1 level) are generated, processing request B is executed before processing request A, and the difference in priority is reduced.

In order to solve the above problems, Japanese Patent Laid-Open No.
There are methods described in JP-A-3361 and JP-A-1-112461.

In the method described in Japanese Patent Application Laid-Open No. 2-143361, the number of times that a specific processing request is overtaken by another processing request while the processing request is in a waiting state, and the count value of the waiting time are set to a predetermined value. When this happens, this particular processing request is selected with the highest priority, so that a processing request from a device with a lower priority is not waited for a long time.

In the method described in Japanese Patent Application Laid-Open No. 1-112461, a priority control is provided with a correction function of judging whether passing is possible, so that a low-priority input / output request does not wait for a long time. I have.

That is, in the method described in the above publication, the execution state of the processing is monitored, and adjustment is performed when the priority balance is about to be lost.

[0014]

However, the above method has a problem that a mechanism for checking the execution state of the queue processing, the waiting time, the count of the number of overtaking processes, and the like must be provided.

Accordingly, it is an object of the present invention to provide an input / output control method in which a difference in priority does not change with the number of queues to be processed.

Another object of the present invention is to provide an input / output control method which does not require a waiting list for each priority level.

Still another object of the present invention is to provide an input / output control method that does not require overtaking monitoring or check control of waiting time.

[0018]

An input / output control method according to the present invention is described as follows. In a computer system that processes a plurality of programs in parallel by time-sharing, an input / output request to the same device requested from a plurality of programs is provided. Is provided with a pointer that points to a specific queue using a processing queue list based on a queue, thereby connecting the queue to a list position corresponding to the priority level, thereby enabling priority control.

The input / output control method according to the present invention is as follows.
`` Registering queues in one list without dividing the list for each priority level, providing a pointer that points to a queue located in the middle of the queue list of lower priority levels registered in the list, and providing queues with higher priority Occurs, the function inserts the generated higher-priority queue at the position before the queue indicated by the pointer and retrieves the queue from the head of the list. "
Having.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described in detail with reference to the drawings.

In this embodiment, in order to execute a certain process, two priority levels P0 and P1 are provided (priority: P0> P1). Do not prepare two waiting lists, but make one. As shown in FIG. 6, a pointer PT pointing to a queue in the list and a flag FL are prepared. Null (NUL: indicates nothing) is set in the pointer PT and "0" is set in the flag FL as initial values.

The case where a processing request has occurred will be described with reference to the flowchart of FIG. As shown in FIG. 7, when a processing request at the P1 level occurs (step S1).
"YES") and link to the end of the list (step S
2) Invert the flag FL (step S3). If the flag FL is “1” (YES in step S4), the pointer PT is updated so as to point to the next processing queue at the P1 level in the list (step S5). Flag F
If L is "0" ([NO] in step S4), the pointer PT is not updated.

The case of executing the processing will be described with reference to the flowchart of FIG. As shown in FIG. 8, when executing the processing, the queue is removed from the head of the processing waiting list, and the request is executed (step S11). If the queue is at the P1 level ("YE" in step S12)
S "), the flag FL is inverted (step S13).
Similarly to the above-described operation, if the flag FL is "1"("YES" in step S14), the pointer PT is updated (step S15).

Therefore, when an operation occurs such that the queue at the P1 level is queued or removed from the list, the PT is updated once every two times and the PT is advanced to the rear of the list. In this manner, the PT points to the queue at the midpoint of the P1 level queue in the list.

When a processing request at the P0 level occurs ("NO" in step S1 in FIG. 10), the queue is not queued at the end of the list, as shown in FIG.
The processing queue is inserted before the queue indicated by T (step S6 in FIG. 10). At this time, no operation is performed on PT and FL. Therefore, the processing request at the P0 level is queued at the midpoint of the list of the processing queue at the P1 level.

When executing the processing, the queue may be removed from the head of the list without considering the priority, and the processing may be performed.

[0027]

In the input / output control method according to the present invention, it is not necessary to divide the processing waiting list for each priority, so that priority control can be realized by a simple method.

Further, there is an effect of controlling that the difference in the priority changes according to the number of queues to be processed. Further, according to the present invention, the queue is linked to a list position corresponding to the priority at the time of queue registration. This eliminates the need for control such as overtaking monitoring for control and checking of waiting time.

[Brief description of the drawings]

FIG. 1 is a block diagram of an input / output control mechanism.

FIG. 2 is a diagram showing a control example of a processing queue list in a conventional example.

FIG. 3 is a diagram showing a control example of a processing queue list in a conventional example.

FIG. 4 is a diagram illustrating a control example of a processing queue list in a conventional example.

FIG. 5 is a diagram showing a control example of a processing queue list in a conventional example.

FIG. 6 is a diagram illustrating a control example of a processing queue list according to the embodiment of the present invention.

FIG. 7 is a diagram illustrating a control example of a processing queue list according to the embodiment of the present invention.

FIG. 8 is a diagram showing a control example of a processing queue list according to the embodiment of the present invention.

FIG. 9 is a diagram illustrating a control example of a processing queue list according to the embodiment of the present invention.

FIG. 10 is a flowchart illustrating an operation when a processing request occurs in the embodiment of the present invention.

FIG. 11 is a flowchart illustrating an operation when a process is executed in the embodiment of the present invention.

[Explanation of symbols]

 1-3: Processing program for making input / output requests 4: Input / output control mechanism 5: Request receiving mechanism 6: Request washing mechanism 7: Request processing mechanism 8: Input / output mechanism

Claims (2)

[Claims] In a computer system for processing a plurality of programs in parallel by time-sharing, an I / O request to the same device requested from a plurality of programs is processed by using a processing queue list based on a queue. An input / output control method having a function of enabling priority control by connecting a queue to a list position corresponding to a priority level by providing a pointer indicating a specific queue. 2. Registering queues in one list without dividing the list for each priority level, providing a pointer to a queue located in the middle of the queue list of lower priority levels registered in the list, An input / output control method that, when a queue with a priority is generated, inserts the generated higher-priority queue at the position before the queue indicated by the pointer and retrieves the queue from the head of the list.